Field of the Invention
This invention relates generally to injection devices for use with an external infusion system for subcutaneous delivery of a selected medication or other therapeutic fluid to a patient, and more particularly to an improved subcutaneous injection set of the type having a soft or flexible cannula, and further including improved sealing means for preventing undesired fluid leakage.
Subcutaneous injection sets are generally known in the art for use in delivering a selected medication or other therapeutic fluid to a desired subcutaneous site located beneath the skin of a patient. Such injection sets commonly include a relatively short cannula or catheter which is supported by and protrudes from a compact housing adapted to receive the infusion fluid via a delivery tube connected suitably to other components of a fluid infusion system.
An insertion needle is normally provided to extend through a lumen formed in the cannula to facilitate transcutaneous placement of the cannula, after which the insertion needle is withdrawn to leave the cannula in place for subcutaneous fluid infusion into the patient. A preferred subcutaneous injection set of this general type is described and claimed in commonly assigned U.S. Pat. No. 4,755,173, which is hereby incorporated herein by reference.
In prior subcutaneous injection sets, the selected infusion fluid is normally supplied to the patient under positive pressure flow conditions. As a result, manufacturing precautions have been required to prevent undesired leakage of the infusion fluid about the exterior of the cannula, and corresponding nondelivery of the infusion fluid to the patient. In the past, attempts to prevent such fluid leakage have included the use of adhesive agents and/or ultrasonic welding or other heat seal techniques intended to sealably fix the cannula to the injection set housing However, such sealing techniques have not provided the desired consistent level of leak-free reliability, possibly due to the use of incompatible materials to form the housing and cannula of the injection set.
There exists, therefore, a significant need for further improvements in subcutaneous injection sets, particularly with respect to providing an improved and reliably sealed mounting arrangement for a soft cannula with respect to an injection set housing. The present invention fulfills these needs and provides further related advantages.